supercharger heads

[What]

I didnt see anything on this subject when i searched, so i was wondering if there are any special considerations when buying heads for a supercharged application. if it makes any difference, its a twin screw supercharger on a 427. thanks

[10thanvhawk]

While there are no ABSOLUTE answers to your question.. PUN INTENDED, there are choices that can help, as with anything modification the more air you put (or push) in the more power you make.

Don't blindly follow the PSI (BOOST) listings as it's all relative to each engine, what we are really talking about is back pressure based upon each engines flow charactoristics. IE: Engine A has blower A with pulley 3.4" , engine B as blower A with pulley 3.4" but has ported heads.
Which one is better? can't tell without knowing the rest..
however if engine B has ported heads the amount of BOOST showing on the meter will be lower even though the blower is exactly the same and the pulley.

As with any Engine combo there are good and bad choices for any item. You don't want a 330 deg cam with stock heads etc.

On to your question, most of us have gone up to higher flowing heads with larger chambers (helps unshroud the valves too) to lower compression, in boosted situations this is a plus The other is port flow and a big plus would be on the EXHAUST side of things where stock heads suffer anyways. You boost in but you don't BOOST OUT, so getting rid of the spend gases is a high priority. Intake wise is debated many ways, some say go with much larger runners due to boost not needing inherent flow design as much as naturaly aspirated engines do. Some say to keep things in check but with a greater portion of flow upgrades on the exhaust, I would agree with the this idea for Centrifical blowers. Porting does help in the lower RPM ranges with Cent types like Vortech and ATI, where they make little boost and generally subtract HP and TQ due to parasitic losses. It takes power to spin these things so they rob more on the bottom since they are not adding any. Then of course a cam to match your setup.

With Roots style its good to go with the exhaust plus all around porting on the intake too.

With turbo you have more of a roots profile but the turbo doesn't boost when not on the pedal.. so all around is a good choice.

so what does it mean?
A good set of ported heads will help, especially if they are ported really well on the exhaust side for boosted applications..

[stonebreaker]

What about ETP's heads? I notice that all of their heads from 225 cc's on up have the same exhaust numbers, pretty much.

Vizard mentions one turbo setup where not only the adjacent intake runners had their shared wall removed, but the heads had their ports siamesed, as well. The engine seemed to respond well to having a large volume of pressurized air available immediately, and screw the intake velocity. I was wondering if using the huge by large 265 cc heads from ETP might do the same thing? That is, the boost would take the place of port velocity on the intake side, and the superb flow of the exhaust port would take care of the extra exhaust flow generated by 10-12 pounds of boost. And then run a very mild 210-220 range cam.
Whach ya'll think?